The palace has dismissed as "fiction" claims Prince Charles was the royal who speculated on the skin colour of the children of the Duke and Duchess of Sussex.
American author Christopher Andersen alleges the prince made the comment on the day Harry and Meghan's engagement was announced in November 2017.
Andersen made the claims in his new book Brothers And Wives: Inside The Private Lives of William, Kate, Harry and Meghan.
He wrote the Prince of Wales said to the Duchess of Cornwall: "I wonder what the children will look like?"
When Camilla replied, "Well, absolutely gorgeous, I'm certain," the book claims Charles went on to say, "I mean, what do you think their children's complexion might be?"
In response, a palace source told Sky's royal correspondent Rhiannon Mills: "This is fiction and not worth further comment."
Andersen stopped short of accusing Prince Charles of being racist, saying "scheming courtiers" gave it a "spin", the New York Post's Page Six reported.
Prince Harry and Meghan accused a member of the Royal Family of racism in claims made during their Oprah Winfrey interview earlier this year.
Meghan said, when she was pregnant with Archie, an unnamed member of the Royal Family raised "concerns and conversations about how dark his skin might be when he's born".
Meghan refused to say who made the comments, adding: "I think that would be very damaging to them."
But the Sussexes later clarified it was not the Queen or the Duke of Edinburgh.
It comes as Charles arrived in Barbados ahead of a historic ceremony that will see the country swear in its first president and formally end the Queen's role as its head of state.